Tires mounted on vehicles are rolled in contact to road surfaces, so that these tires are expendable supplies in which tread parts are worn away while the tires are traveling. Accordingly, such tires are desired which own superior abrasion characteristics within a range in which the tread parts of those tires do not sacrifice other performance (e.g., steering performance, and vibration riding comfort performance).
Generally speaking, an abrasion characteristic of a tread part of a tire, for instance, an abrasion amount of the tread part is determined by a sliding amount of the tread part which partially slides with respect to a road surface and an abrasion resistance material of a rubber contained in the tread part.
In general, it is known that abrasion ratios of a tread part under operating conditions are arranged in the following order from the largest abrasion ratio: the abrasion ratio during a cornering operation, the abrasion ratio during a breaking operation, and the abrasion ratio during a driving operation.
On the other hand, during a cornering operation in which an abrasion ratio is large, a sliding amount of the tread part with respect to a road surface is not exclusively determined based on a slip angle. That is, this sliding amount is determined not only based on an adhesive friction coefficient and a sliding friction coefficient of the tread part, but also a structure of a belt part and a structure of a side part.
Also, during a breaking operation in which an abrasion ratio is relatively large, a sliding amount of the tread part with respect to a road surface is not exclusively determined based on a slip ratio during the braking operation. That is, this sliding amount is determined not only based on an adhesive friction coefficient and a sliding friction coefficient of the tread part, but also a structure of a belt part and a structure of a side part.
Meanwhile, in a case where an abrasion characteristic of a tire is predicted, the prediction is evaluated based on a material breaking characteristic of rubber used in a tread part, and a result of an indoor-laboratory test (i.e., abrasion amount measuring test) of the rubber. As the indoor-laboratory test, for instance, various sorts of testing methods described in the newly published JIS (Japanese Industrial Standard) K6264 are used.
However, as previously described, an abrasion characteristic of a tread part in a tire is not influenced only by a rubber material of the tread material. The abrasion characteristic is influenced by not only the adhesive friction coefficient and the sliding friction coefficient of the tread part, but also the structure of the belt part and the structure of the side part. Thus, the abrasion characteristic of the tire is not predicted with high precision only by the evaluation of the rubber material. In a case where an abrasion test is carried out using an actual vehicle, the abrasion characteristic is predicted with high precision. However, there is a problem that lengthy testing time is necessarily required.